University of Guilan Caspian Journal of Environmental Sciences 1735-3033 21 1 2023 01 01 Effects of bacterial isolate, Priestia megaterium HB8 and its filtrate on Controlling the root-knot nematode, Meloidogyne incognita 105 114 6200 10.22124/cjes.2023.6200 EN Hadeel Badri Dawood Department of Plant Protection, Agricultural Engineering Sciences Collage, University of Baghdad, Iraq Saad Tareq Abdul Malek Yass Department of Plant Protection, Agricultural Engineering Sciences Collage, University of Baghdad, Iraq Journal Article 2023 02 01 This study was conducted to isolate biological control agents from soil samples surrounding the roots of uninfected cucumber, watermelon, eggplant, tomato, and okra plants in fields infested with root-knot nematodes and to evaluate their effectiveness. Therefore, fifteen bacterial isolates were selected to study their effects on the vitality of the second stage juveniles (J2) of the root-knot nematode, <em>Meloidogyne incognita</em>. Nine bacterial isolates showed a mortality rate of juveniles ranged between 80 and 100%, while isolate HB8 was unique in having a high ability to influence the vitality of the juveniles, as the mortality rate reached 100%. This isolate was chosen to test its effectiveness in inhibiting egg hatching. The results showed that the inhibition rate after 72 h of incubation reached 94.33%. The effect of the bacterial filtrate of isolate <em>Priestia megaterium</em> HB8 was tested using three concentrations (10, 20, and 30%) on the mortality rate of J2 and the inhibition rate of egg hatching. Moreover, the 30% concentration exhibited a high ability to increase the mortality rate of a juvenile to 97.66% after 48 h of incubation, while the inhibition rate of egg hatching was 96.66% after 72 h. https://cjes.guilan.ac.ir/article_6200_4f3dbd2c26309e7a03c856cba2f183e3.pdf